Hydrocarbon separations



United States Patent 3,518,322 HYDROCARBON SEPARATIONS Rodney D. Beckham, Bridgeton, George D. Davis, Creve Coeur, and Earle C. Makiu, Jr., St. Louis, Mo., assignors to Monsanto Company, St. Louis, Mo., a corporation of Delaware N0 Drawing. Filed July 29, 1968, Ser. No. 748,240 Int. Cl. C07c 7/16 US. Cl. 260-674 17 Claims ABSTRACT OF THE DISCLOSURE A process for the separation and recovery of aromatic hydrocarbons from admixture with unsaturated aliphatic hydrocarbons by means of selective complex formation using cuprous fluoroborates or cuprous fluorophosphates as the complexing agent.

BACKGROUND OF THE INVENTION The present invention relates to a process for the separation, purification and recovery of certain hydrocarbons. More particularly, the present invention relates to a process for the separation and recovery of aromatic hydrocarbons from admixture with unsaturated aliphatic hydrocarbons.

One of the most difiicult hydrocarbon separations to accomplish is the separation of olefins and/or diolefins from aromatic hydrocarbons. It has been proposed to effect this separation by selective absorption, selectice adsorption, extractive distillation, azeotropic distillation and the like. However, none of the proposed means of separating unsaturated aliphatic hydrocarbons from aromatic hydrocarbons have achieved any significant measure of success. In general, selectivity or capacity has been poor or, in many instances, economics are very unfavorable.

It is an object of the present invention to provide a new and improved process for the separation of hydrocarbons. It is another object of the present invention to provide a process for the separation of aromatic hydrocarbons from unsaturated aliphatic hydrocarbons. Another object of the present invention is to provide a new and improved process for the separation of olefin and/or diolefin hydrocarbons from aromatic hydrocarbons. An additional object of the present invention is to provide a process for the separation of olefin and/ or diolefin hydrocar-bons from admixture with aromatic hydrocarbons by means of selective complex formation. A remaining object of the present invention is to provide a process for the separation of olefin and/ or diolefin hydrocarbons from admixture with aromatic hydrocarbons by selectivity complexing the olefin and/ or diolefin hydrocarbons from said mixture and a means for recovering the com plexed olefin and/ or diolefin hydrocarbons from the complex. Additional objects will become apparent from the following description of the invention herein disclosed.

SUMMARY OF THE INVENTION The present invention, which fulfills these and other objects is a process for the separation of unsaturated aliphatic hydrocarbons from admixture with aromatic hydrocarbons which comprises contacting such a mixture with a first complex comprising a cuprous salt selected from the group consisting of cuprous fiuoroborate and cuprous fluorophosphate and a hydrocarbon selected from the group consisting of olefin hydrocarbons, aromatic hydrocarbons, and mixtures of olefin and aromatic hydrocarbons, thereby forming an extract phase and a ralfinate phase, separating said extract and said rafiinate phase, and recovering from said extract phase a hydro- 3,518,322 Patented June 30, 1970 carbon fraction containing unsaturated aliphatic hydrocarbons in a substantially higher weight ratio to aromatic hydrocarbons than the original feed mixture and recovering from said rafiinate phase a hydrocarbon fraction containing aromatic hydrocarbons in a substantially higher weight ratio to the unsaturated aliphatic hydrocarbons than in the original feed mixture.

While recovery of the unsaturated aliphatic hydrocarbons from the extract phase may be accomplished by the use of vacuum, heat, or the like, it is usually preferred to displace such hydrocarbons from the extract by contacting said extract with unsaturated aliphatic hydrocarbons of a molecular Weight diiferent from those in the extract or, in the alternative, with vinyl aromatic hydrocarbons. The amount of such hydrocarbons used to displace unsaturated aliphatic hydrocarbons from the extract phase is at least a molar equivalent.

It is frequently desirable to employ a non-complexible hydrocarbon diluent or solvent as an aid to formation of the extract and rafiinate phases and/or for further extracting the extract phases formed in the present process to remove from such extract phases the hydrocarbons which are not complexed with the cuprous salt. For example, a non-complexible hydrocarbon such as a lower molecular weight parafiin hydrocarbon, i.e., hexane may be introduced into contact with the first complex concurrently with the mixture of unsaturated aliphatic hydrocarbons and aromatic hydrocarbons. The use of such a non-complexible hydrocarbon diluent results in a more rapid phase formation as well as in more efiicient removal of non-complexed feed materials from the extract phase to the railinate phase thereby producing an extract phase richer in the complexible unsaturated aliphatic hydrocarbons than is obtained without the use of the non-complexible diluent. The use of the non-complexible hydrocarbon diluent or solvent as a further extractant of the extract merely comprises contacting the extract phase with the non-complexible hydrocarbon solvent to thereby absorb in the solvent non-complexed feed hydrocarbons which may be present in the extract phase.

By means of the process of the present invention, olefin and/or diolefin hydrocarbons may be selectively removed from admixture with aromatic hydrocarbons. This process provides for very high selectivity and yet retains a relatively high capacity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further describe the present invention, particularly with respect to the preferred embodiment thereof, the following examples are presented.

EXAMPLE I A first complex was prepared by dispersing 63.5 grams of powdered metallic copper along with 137.5 grams of CuF -2H O in 644 grams of toluene and then continuously introducing gaseous BF into the dispersed medium until all solids had solubilized. The reaction mass was maintained at a temperature of approximately 110 C. and continuously agitated throughout the addition of the ER, with continuous removal of the water generated. Agitation was continued for a period of several minutes and the product cooled back to ambient temperatures (73- 75 F). The resulting first complex was contacted With a hydrocarbon mixture consisting of 6.2 grams of hexene-l (30.85 percent by weight) and 13.9 grams of henzene (69.15 percent by weight) at a temperature of approximately 25 C. To the resulting mixture was added 16.1 grams of 2,3-dimethylbutane to induce phasing. The amount of first complex used was approximately 21.4 grams. A raffinate and extract phase formed and were separated and analyzed. The percent by weight of hexene-l and benzene in both the rafiinate and extract phases on a toluene, CuBF and 2,3-dimethylbutane free basis is presented in the following table:

Component Rafiinatc Extract Hexene-l 20. 18 64. 55 Benzene 79. 82 35. 45

The efficiency of the present process is apparent from consideration of the significant increase in concentration of the hexene-l in the extract as compared to the original feed and with only a single stage contacting. This concentration increased from 30.85% by weight to 64.55% by weight or an increase of approximately 109.24%.

EXAMPLE II Component Raflinate Extract Octane-l 39. 4 73. 4 Ethylbcnzene 66. 6 26. 6

EXAMPLE III To demonstrate the recovery of olefin hydrocarbons from the extract phase with an olefin hydrocarbon of a different molecular weight, a hexene-l containing extract similar to that obtained in Example I above, was intimately contacted with pentene-l at a temperature of 25 C. The amount of pentene-l used was sufiicient to produce a Weight ratio of pentene-l to hexene-l in the extract phase of 2:1. Extract and raffinate phases formed and were separated. The extract phase was again contacted with pentene-l in a weight ratio of 2:1, pentene-l to hexene-l. Again, a rafiinate and extract phase formed and were separated. The percent by weight of hexene-l in the final extract was 8.7 whereas the original extract from which the hexene-l was recovered contained 27.8% by weight hexene-l. Therefore, approximately 68.6% by weight of the available hexene-l was recovered from the extract by the two-stage contact with pentene-l.

EXAMPLE IV A cuprous fiuorophosphate first complex is prepared by dispersing 137.5 grams of CuF -2H O and 63.5 grams of powdered metallic copper in 644 grams of toluene and continuously introducing phosphorous pentafiuoride until all solids are solubilized. The reaction mass is continuously agitated throughout the preparation of the first complex and maintained at a temperature within the range of 80 to 110 C. After all solids are solubilized, approximately 480 grams of sulfolane is added, thereby forming two phases which are then separated. The extract phase represents the first complex.

With the cuprous fluorophosphate containing first complex prepared above, 1:1 by weight mixture of metaxylene and octene-Z is contacted at a temperature of approximately 25 C. and at autogenous pressure. The weight ratio of cuprous fiuorophosphate in the first complex to the octene-2 in the hydrocarbon mixture is approximately 321. Extract and rafilnate phases form and are separated. The raflinate phase is found to contain a substantially higher ratio of meta-xylene to octene-2 than the original feed mixture, Conversely, the extract phase is found to contain a substantially higher ratio of octene- 2 to meta-xylene than the original mixture.

EXAMPLE V To demonstrate operation of the process of the present invention as a continuously operating process, a hydrocarbon mixture consisting of by Weight hexene-l and 50% by weight benzene is continuously separated in an extraction column having approximately 20 perforated trays, each tray capable of operating at approximately 50% theoretical tray efficiency. A first complex is continuously introduced onto the top of the 20th tray from the bottom of the extraction column. This first complex is one prepared as follows: powdered metallic copper and CuF -2H O are dispersed in toluene, the weight ratio of Cu to CuF -2H O to toluene being 122.2:10. Gaseous BF is then passed through the mixture until it is completely in liquid phase. The reaction mass is maintained at a temperature of approximately 110 C. and continuously agitated throughout addition of the BE, with continuous removal of the water generated. The agitation is continued for several minutes beyond the period of BF addition and the product cooled to ambient temperatures (73-75 F.).

Concurrently with introduction of the first complex into the top of the extraction column, the above-defined hydrocarbon feed mixture is continuously introduced into the column between the 10th and 11th tray and n-heptane is continuously introduced below the first tray. The column is operated at a temperature within the range of to F. and at autogenous pressure. The Weight ratio of first complex to feed mixture to n-heptane is 2.2: 1 :0.5. A rafiinate, termed the first rafiinate, is continuously taken overhead from the extraction column and an extract, termed the first extract, is continually taken from the bottom. The raffinate contains benzene and hexene-l in a weight ratio of 24:1. The extract contains benzene and hexene-l in a weight ratio of 24:1 and contains approximately 96% of the hexene-Z present in the original mixture and about 4% by weight of the benzene present in such original mixture.

The extract from the extraction column is continuously introduced into a second extraction column of approximately 20 plates adjacent a top plate thereof. Pentene-l is continuously introduced into the second extraction column adjacent the bottom thereof, the weight ratio of the extract from the first extraction column to the pentene-l being approximately 1:1. The second extraction column is operated at substantially the same temperatures and pressures as the first column. A rafiinate, termed the second raffinate, is continuously taken overhead from the second extraction column and an extract, termed the second extract, is continuously taken from the bottom. The second raffinate contains hexene-l and benzene in a weight ratio of 23:1. The extract has the composition of 39.3% by weight CuBF 24.1% by weight toluene, 2.6% by weight hexene-l and 34.0% by weight pentene-1. The extract from the second extraction column is recycled back to the first extraction column as a part of the first complex introduced therein.

The cuprous salts employed in forming the complexes used in carrying out the process of the present invention are cuprous tetrafluoroborate and cuprous hexafluorophosphate. Generally, these are referred to as cuprous fluoroborate and cuprous fluorophosphate. Both of these salts are relatively unstable and cannot be readily formed as the salt. As a result, the usual practice is to form the salt in the presence of an organic compound with which the salt will complex, thereby forming the salt and the complex of the salt with the organic compound almost concurrently.

The organic compounds in which the cuprous salts may be formed and with which such salts are immediately complexed may include any of a rather large number of s ch compounds. The choice of the particular organic compound is often dictated by the hydrocarbons in the hydrocarbon mixture to be separated. Generally, however, the organic compounds will be aromatic hydrocarbons. Such aromatic hydrocarbons may contain a single aromatic ring or may contain two or more aromatic rings, either condensed or non-condensed. In addition, the aromatic hydrocarbons may have substituents to the rings or may be condensed with one or more other ring structures which are parafiinic or olefinic in nature. Non-limiting examples of aromatic hydrocarbons suitable for use in preparing the cuprous salts of the present invention are benzene, toluene, the xylenes, various other polymethylbenzenes, such as mesitylene, isodurene, tri-, tetra-, pentaand hexamethylbenzenes, ethylbenzene and the various polyethylbenzenes, isopropylbenzenes, the various butyl and pentylbenzenes and the like, the substituted benzenes containing two or more different substituents such as ethyltoluene, isopropyltoluene, and ethylxylenes; naphthalene, the various methylnaphthalenes, and polymethylnaphthalenes, ethylnaphthalene and the various polyethylnaphthalenes, the naphthalenes containing propyl, isopropyl, butyl, and pentyl substituents; the substituted naphthalenes containing two or more different substituents such as methylethylnaphthalene, methylpropylnaphthalenes, etc.; the dihydronaphthalenes such as methyl, ethyl, propyl, and butyl substituted dihydronaphthalenes; the tetrahydronaphthalenes such as methyl, ethyl, propyl, and pentyl substituted tetrahydronaphthalenes and the like. In the preferred practice of the present invention, the aromatic hydrocarbons most often employed as the organic compound in forming the complexes of the present invention are benzene, naphthalene, partially hydrogenated naphthalenes, and the various alkyl substituted derivatives of these wherein the alkyl substituents have no more than four carbon atoms per substituent. Within this group of preferred aromatic hydrocarbons are such compounds as benzene, ethylbenzene, toluene, the xylenes, naphthalene and the methylnaphthalenes, dihydronaphthalenes and tetrahydronaphthalenes. A particularly useful group of aromatic hydrocarbons for use in forming the complexes is that including such compounds as toluene, ethylbenzene, ethyltoluene, the xylenes and tetrahydronaphthalene.

The method of preparing the cuprous fiuoroboratearomatic hydrocarbon containing complex, referred to herein are the first complex, which is used for the separation of hydrocarbon mixtures in accordance with the present invention may be any of those methods conventionally used. In US. Pat. 2,953,589, the preparation of cuprous fiuoroborate-aromatic hydrocarbon complexes by the introduction of powdered copper, BF and anhydrous HF into benzene or other aromatic hydrocarbons is disclosed. This method may be used for the purposes of the present invention. In addition, the cuprous fluoroborate-aromatic hydrocarbon complex may be prepared by dispersing CuF -2H O and metallic copper in an aromatic hydrocarbon and heating the reaction mixture while introducing gaseous BF into the dispersed medium. This method is described in Journal of the American Chemical Society, vol. 74, p. 3702, 1952. This latter described method is preferred for the practice of the present invention. In addition to these two methods of preparing the cuprous fluoroborate-aromatic hydrocarbon complex, any other of the methods known to those skilled in the art may be used.

Preparation of the cuprous fluorophosphate-aromatic hydrocarbon complex may be by any of those means known to those skilled in the art. Preferably, however, this complex is prepared by introducing anhydrous CuF or CuF -2H O, metallic copper and phosphorous pentafluoride into an aromatic hydrocarbon medium and heating with agitation to an elevated temperature in excess of 75 C. The cuprous fiuorophosphate-aromatic hydrocarbon complexes may on occasion be solid at room temperature and therefore, must be maintained at elevated temperatures for use in the process of the present invention or, in the alternative, be used along with a suitable solvent. It is believed that impurities in the system cause these complexes to be solid. A number of solvents suitable for maintaining the cuprous fluorophosphate in solution will be discussed below. In addition to the above method of preparing the cuprous fluorophosphate-aromatic hydrocarbon complex, any other method known to the art may be used.

As mentioned above, in many instances to avoid the use of elevated temperatures, it is desirable to use a solvent in the preparation of the cuprous fluorophosphate containing first complex. Such solvent includes a wide range of organic solvents particularly those containing oxygen and/ or sulfur. Ethers, ketones, sulfones, disulfides, thioethers, thioureas, nitro alkyl and aryl, trihydrocarbonyl phosphines and the like represent classes of useful solvents. While the particular solvent selected is primarily a matter of individual choice, it is somewhat preferred that the solvent be one selected from the group consisting of the alkyl and aryl sulfones, particularly such compounds as sulfolane and alkyl sulfolanes.

In preparing the cuprous salt-organic compound first complexes for use in the separations processes disclosed herein, some care should be exercised in the selection of the organic compound to avoid use of an organic compound which itself will be difficultly separable from hydrocarbons of the mixture to be separated. Each mole of the cuprous salt-organic compound first complexes formed in accordance with the present invention generally will contain at least two moles of organic compound and one mole of the cuprous salt. Separation of hydrocarbon mixtures in accordance with the processes disclosed herein involves the displacement of one or more of the moles of organic compound from the first complex and substitution therein of the unsaturated aliphatic hydrocarbon components of the hydrocarbon mixture to be separated. Since the organic compound displaced from the first complex by the unsaturated aliphatic hydrocarbon components of the mixture generally mix freely with the components of the feed mixture which do not complex with the cuprous salt, the organic compound of the first complex should be one which is readily and simply separated from the non-complexed hydrocarbons of the hydrocarbon mixture to be separated. To illustrate the above, if the hydrocarbon mixture to be separated is one comprised of octene-l and meta-xylene, it would not be desirable to use para-xylene as the organic compound in which the first complex is formed. If for instance, para-xylene was used as the organic compound, the raffinate resulting from contact of the first complex with the mixture of octene-l and meta-xylene would contain a mixture of metaand para-xylene which compounds are difliculty separable from one another.

The amount of the first complex used in carrying out the separation of unsaturated aliphatic hydrocarbons from aromatic hydrocarbons in accordance with the process of the present invention may vary considerably. However, in general, as the mole ratio of available cuprous salt in the first complex to unsaturated aliphatic hydrocarbons goes down, the selectivity of the cuprous salt for certain of the olefin hydrocarbons increases. Therefore, the optimum amount of first complex used will vary according to the olefin hydrocarbon mixture to be separated and the particular separation which it is desired to carry out. In general, however, the amount of first complex most often employed in such as to provide a mole ratio of the cuprous salt (CuBR, or CuPF to the unsaturated aliphatic hydrocarbons in the mixture to be separated within the range of 0.1 :1 to 2:1. Preferably, however, the amount will be such as to provide a mole ratio of cuprous salt to available unsaturated aliphatic hydrocarbons within the range of 0.25:1 to 1:1.

It has been found particularly useful in carrying out the separations process of the present invention to use a non-complexible hydrocarbon diluted or solvent to aid in the formation of extract and raffinate phases and/or for further extraction of the extract phases to remove from such phases hydrocarbons which are not complexed with the cuprous salt. The use of such non-complexible hydrocarbons as an aid to phase formation is exemplified in the above examples. In most instances, the non-complexible hydrocarbon employed is an aliphatic hydrocarbon of 3 to 15 carbon atoms. Non-limiting examples of such hydrocarbons are propane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, isobutane, isopentanes, iodoheptanes, isodecanes, isododecanes, isotridecanes, cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, and the like. Most often, the saturated aliphatic hydrocarbons are paraffinic hydrocarbons and may be straight-chain or branched-chain. The most useful saturated aliphatic hydrocarbons are the parafiinic hydrocarbons of 4 to 7 carbon atoms per molecule. In selecting the particular noncomplexible hydrocarbon diluent or solvent to use as above-described, care should be exercised to avoid selecting one which itself is difficultly separable from components of the system with which it will be mixed.

The amount of non-complexible hydrocarbons employed in the process of the present invention may vary considerably. The actual amount of such hydrocarbons used will depend to a large extend on the amount of hydrocarbons in the mixture to be saparated which will not be complexed with the cuprous salt and on the degree of separation desired. Usually, however, about 0.25 to 5 volumes of the non-complexible hydrocarbon is used per volume of aromatic hydrocarbons in the feed mixture with which is to be separated.

Conditions of temperature and pressure whereby the separations process of the present invention may be successfully practiced may vary rather widely. Most often, however, the process of the present invention will be practiced at temperatures within the range of to 195 C., preferably, within the range of 25 to 150 C. The pressures employed for practicing the process of the present invention do not appear to be critical and may range from subatmospheric pressures to superatmospheric pressures. As a practical matter, it is usually desirable to operate at or near atmospheric pressure, the pressures ranging from as low as 50 mm. Hg to as high as 250 p.s.i.g. and higher.

The process described herein provides for the separation of unsaturated aliphatic hydrocarbons from aromatic hydrocarbons. Such separations include the separation of olefin and/or diolefin hydrocarbons from aromatic hydrocarbons. The molecular weight range of such hydrocarbons includes those varying from carbon atoms (pentanes and pentadiene) to hydrocarbons having carbon atoms and higher. Generally, any mixture of unsaturated aliphatic hydrocarbons and aromatic hydrocarbons which is liquid or liquefiable under the above defined conditions of separation may be successfully separated in accordance with the present invention. Liquefiable hydrocarbons include those which may be liquid at the elevated temperatures permissible in operating the separations process of the present invention. Liquefiable hydrocarbons also include those which are liquefiable by mutual solubility with other components of the system or by solvents inert to the separations process. Such separations as the separation of hexenes from benzene, heptenes and/or heptadienes and/or certain C olefin and diolefin hydrocarbons from toluene, certain C hydrocarbons such as octenes and the like from ethylbenzene, ortho-, meta-, and paraxylenes and the like, may be carried out through the present separations process.

While the unsaturated aliphtic hydrocarbons contained in the extract phase may be recovered therefrom by means such as heat, reduced pressure, and the like, it is preferred to displace these hydrocarbons from the extract phase by means of other hydrocarbons. Such other hydrocarbons useful in displacing the unsaturated aliphatic hydrocarbons from the extract phase are vinyl aromatic hydrocarbons and other unsaturated aliphatic hydrocarbons, generally of a molecular weight different from the unsaturated aliphatic hydrocarbons in the extract phase. Among the vinyl aromatic hydrocarbons useful for displacing unsaturated aliphatic hydrocarbons from the extract phase are such compounds as styrene, alpha methyl styrene, vinyl toluene and the like. The unsaturated aliphatic hydrocarbons useful include those having as high as 20 carbon atoms and higher, again generally being those that are liquid or liquefiable at slightly elevated temperatures or by the use of solvents inert to the system or by mutual solubility with the components of the extract phase. Most often, the unsaturated aliphatic hydrocarbons employed are olefin hydrocarbons having less than 15 carbon atoms. In choosing the vinyl aromatic hydrocarbons or unsaturated aliphatic hydrocarbons for displacing the extracted components from the extract phase, again, care should be used that the hydrocarbon selected is not one which will itself by difiicultly separable from other hydrocarbon components of the system.

What is claimed is:

1. A process for the separation of unsaturated aliphatic hydrocarbons from aromatic hydrocarbons, said process comprising contacting a mixture of unsaturated aliphatic hydrocarbons and aromatic hydrocarbons with a first complex which comprises a complex of a cuprous salt selected from the group consisting of cuprous fiuoroborate and cuprous fiuorophosphate and a hydrocarbon selected from the group consisting of aromatic hydrocarbons, olefin hydrocarbons of a molecular weight different from those of said unsaturated aliphatic hydrocarbons in said mixture and combinations of such aromatic hydrocarbons and olefin hydrocarbons, thereby forming an extract phase and a rafiinate phase, separating said extract and rafiinate phase, recovering from said extract phase a hydrocarbon fraction substantially richer in said unsaturated aliphatic hydrocarbons than the original hydrocarbon mixture, and recovering from said rafiinate phase a hydrocarbon fraction substantially richer in aromatic hydrocarbons than said original hydrocarbon mixture.

2. The process of claim 1 wherein the cuprous salt is cuprous fluoroborate.

3. The process of claim 1 wherein the first complex comprises cuprous fiuoroborate and an aromatic hydrocarbon.

4. The process of claim 3 wherein the aromatic hydrocarbon is selected from the group consisting of benzene, naphthalene, partially hydrogenated naphthalenes, the alkyl substituted derivatives of these wherein the alkyl substituents have no more than 4 carbon atoms per substituent, and mixtures of these.

5. The process of claim 4 wherein the aromatic hydrocarbon is toluene.

6. The process of claim 1 wherein said mixture is contacted with said first complex at a temperature within the range of 0 to C.

7. The process of claim 1 wherein the unsaturated aliphatic hydrocarbons are olefin hydrocarbons.

8. The process of claim 1 wherein the unsaturated aliphatic hydrocarbons are diolefin hydrocarbons.

9. The process of claim 1 wherein the unsaturated aliphatic hydrocarbons have 5 to 20 carbon atoms per molecule.

10. The process of claim 1 wherein said unsaturated aliphatic hydrocarbons are recovered from said extract phase by contacting said extract phase with vinyl aromatic hydrocarbons, said vinyl aromatic hydrocarbons being in an amount at least equimolar to the unsaturated aliphatic hydrocarbons within said extract phase.

11. The process of claim 1 wherein said unsaturated aliphatic hydrocarbons are recovered from said extract phase by contacting said extract phase with an amount of an unsaturated aliphatic hydrocarbon of a molecular weight difierent to that in said extract phase, the amount of such unsaturated aliphatic hydrocarbon with which the extract phase is contacted being at least equimolar to the amount of unsaturated aliphatic hydrocarbons within the extract phase.

12. The process of claim 1 wherein said mixture of unsaturated aliphatic hydrocarbons and aromatic hydrocarbons is contacted with said first complex in the presence of a non-complexible hydrocarbon.

13. The process of claim 12 wherein said non-complexible hydrocarbon is a saturated aliphatic hydrocarbon of 3 to 15 carbon atoms.

14. The process of claim 1 wherein said first complex is present in an amount such as to provide a mole ratio of cuprous salt in the unsaturated aliphatic hydrocarbons to be selectively complexed with said cuprous salt within the range of 0.1:1 to 2:1.

15. The process of claim 1 wherein said first complex comprises cuprous fiuoroborate, an aromatic hydrocarbon and an olefin hydrocarbon.

16. The process of claim 15 wherein the aromatic hydrocarbon is selected from the group consisting of henzene, naphthalene, partially hydrogenated naphthalenes, the alkyl substituted derivatives of these wherein the alkyl substituents have no more than 4 carbon atoms per substituent, and mixtures of these.

17. A process for the separation of unsaturated aliphatic hydrocarbons from aromatic hydrocarbons, said process comprising introducing a mixture of such hydrocarbons into a first extraction column intermediate the ends thereof, concurrently introducing adjacent the top of said extraction column a first complex comprising a cuprous salt selected from the'group consisting of cuprous fiuoroborate and cuprous fluorophosphate and a hydrocarbon selected from the group consisting of aromatic hydrocarbons, olefin hydrocarbons and mixtures of olefins and aromatic hydrocarbons, concurrently introducing into said extraction column adjacent the bottom thereof a non-complexible hydrocarbon, removing overhead from said first extraction column a first raflinate containing a hydrocarbon fraction substantially richer in aromatic hydrocarbons than the original hydrocarbon mixture, removing from the bottom of said extraction column a first extract phase, introducing said first extract phase into a second extraction column intermediate the ends thereof, concurrently introducing a hydrocarbon selected from the group consisting of unsaturated aliphatic hydrocarbons of a molecular weight different from those of said hydrocarbon mixture and vinyl aromatic hydrocarbons, said hydrocarbon being introduced in a quantity which is at least in molar equivalent to the unsaturated aliphatic hydrocarbons in said first extract phase, concurrently introducing non-complexible hydrocarbons into said second extraction column, removing from the bottom of said second extraction column a second extract phase at least a portion of which is recycled to said first extraction column as at least a portion of said first complex, removing overhead from said second extraction column a second raffinate phase containing a hydrocarbon fraction substantially richer in the unsaturated aliphatic hydrocarbons of said original hydrocarbon mixture than was said original hydrocarbon mixture.

References Cited UNITED STATES PATENTS 2,953,589 9/1960 McCaulay 260674 DELBERT E. GANTZ, Primary Examiner C. R. DAVIS, Assistant Examiner US. Cl. X.R. 260-677, 681.5 

